The invention relates to a circuit arrangement comprising an amplifier and an electronic selector switch at the input of an amplifier for switching to one out of a plurality of transmission paths.
In Dietrich Elias, "Telekommunikation in der Bundesrepublik Deutschland 1982", R. v. Decker's Verlag, G. Schenck, Heidelberg, Hamburg, 1982, pages 206-208, a line terminating unit for a PCM-transmission system is described. The line terminating unit comprises an automatically controlled interface amplifier which equalizes the incoming distorted PCM signals. The attenuation on the line may be up to 12 dB at 70 MHz. An electronic selector switch, which can be controlled either manually or remotely, is provided at the input of the interface amplifier so as to ensure that when required, a switch from the operating line to a substitute line can be made.